1. Field of the Invention
The present invention relates generally to a wireless power transmission system, and more particularly, to a power transmitting method for communication with a power receiver in a wireless multi-power transmission system.
2. Description of the Related Art
A wireless power transmission system typically includes a power transmitter and a power receiver. Power transmission between the power transmitter and the power receiver is configured such that power is transferred between a first coil of the power transmitter and a second coil of the power receiver. Such a configuration is commonly used in various power transmission systems.
A communication technique used in the wireless power transmission system having the above configuration may be divided into two schemes. One such scheme is an In-Band communication scheme that performs communication through a coil that transfers power, and the other such scheme is an Out-Band communication scheme that performs communication through a communication end that is separate from the coil that is transferring power.
The wireless power transmission system employing such wireless charging technologies includes a power transmitter in a form of a power supplying supporter, and is configured such that the power transmitter supplies power to the power receiver such as a mobile terminal. A wireless power transmission system can also be configured such that wireless charging between power receivers is possible by sharing a battery installed in the power receiver even without the power supplying supporter. As described above, when the wireless charging between the power receivers is possible, the power receivers can be operated without power transferred from the power transmitter. However, most power receivers are operated by power received from the power transmitter such as the power supplying supporter.
However, when the power receiver is operated by power supplied from the power transmitter while performing communication according to the Out-Band communication scheme, if sufficient power is not supplied from the power transmitter, the power receiver may not operate normally. For example, when the power receiver is not fully located within an effective area where the power receiver can receive power transferred from a nearby power transmitter, or when a plurality of power receivers are located in the effective area so as to share power for communication from the power transmitter at the same time, it may not be possible for all power receivers to obtain equal charging efficiency and power transmission efficiency is also deteriorated. Accordingly, some of or all of the power receivers may not receive sufficient power.
Accordingly, a power receiver that does not normally receive sufficient power may not be able to perform communication. When the power transmitted is not sufficient to perform communication with the power receiver, the power transmitter does not supply power to the power receiver and may not recognize the power receiver as a valid receiver.